Hacker News Reader

Just to add to the sibling comment. To maintain backwards compatibility, OCaml 5 has both threads and domains.

Threads belong to a domain and only one thread can hold the runtime lock for the domain. This is the same behaviour as in OCaml 4.

With OCaml 5 you can have as many domains as you want though (we recommend no more than you have cores though).

View on HN

This backwards compatibility decision to separate threads from domains has been very useful and allows to gradually "port" existing code to 5.0: first just fixup C bindings to avoid naked pointers, and then code can safely run on OCaml 5 just as before.

And once a program (and all its dependencies) have removed dependence on global state they can opt-in to multicore by spawning additional domains.

Reply on news.ycombinator.com